1. Field of the Invention
The present invention relates to a gas shut-off valve assembly that automatically closes off gas flow in a gas conduit in response to a seismic vibration to prevent undesired gas leakage. The assembly remains closed until manually reset to its original open position.
The present invention also relates to a method of automatically maintaining a gas conduit in a closed position in response to a seismic vibration using a gas shut-off valve assembly to prevent undesired gas leakage.
2. Description of Prior Art and Related Information
Thousands of earthquakes occur around the world every year. Although most of the earthquakes are unnoticed because they are too weak on the Richter scale or occur in the remote areas of the world, major earthquakes are known to cause devastating damages that often result in the loss of life and property. In many cases, the damages are caused by destructive fires that break out uncontrollably due to ruptured gas pipes. For example, the major San Francisco earthquake of 1906 ruptured the city's main gas lines, destroying over 80% of the city and killing over 3,000 people due to devastating fires that lasted for days.
Various methods to shut off gas flow in conduits and pipelines in response to earthquake vibrations are known in the art. These methods generally share the common features of placing a gas valve in a section of a gas pipeline, maintaining the gas valve in an initial open position, and triggering the gas valve to close the flow of gas in the pipeline upon sensing significant seismic forces.
Typically, the gas valve used for such purposes rotates around an axis and operates in a manner similar to a flapper, such that when an earthquake occurs, the valve is triggered to swing downward and close the section of the pipeline to cut off gas flow. However, the gas valves known in the art use the assistance of a spring mechanism to push down on the valve to close the valve and maintain the section of the pipeline closed. Over time, the spring loses its rigidity and fails to maintain the section of the pipeline closed, resulting in unwanted gas leakage.
The object of the present invention is to provide a springless gas valve assembly that automatically shuts off gas flow in a gas pipeline upon a significant seismic vibration until the valve is manually reset to its original open position, thereby reducing the occurrences of gas leakage commonly associated with spring failure in conventional gas valves.